Hi, I recently put in a JDM H23a engine in my 94 prelude Si. All is good except for one problem when in 1st or 2nd gear at very low rpm with the clutch out and not touching the gas pedal the engine will go to just about a stall and then pick up to 2000 or so then jump right back down. It does this so fast that it will chirp the tires when it does this. Ive changed over most of the sensors and valves from the usd manifold but still has not fixed the problem. I dont know if I have a vacuum hose or 2 wrong or if there is a sensor bad or if something is gummed up inside the manifold or throttle body, I have new gaskets to tear it apart clean and reassemble but I figured id ask all you guys if ya have any input. Thanks Dylan

 

tps or idle control valve needs to be replaced

 

also, take your intake tubing off the TB, and open up the TB butterfly (?) and see if it's black in there. if it is, get some TB cleaner (i used Seafoam CF cleaner from pepboys) and get a tooth brush, and a rag and clean it out. just did it to mine last night, and no more idle surge.